The present invention relates to an apparatus for generating gas for inflating a vehicle occupant restraint which restrains movement of an occupant of a vehicle in the event of a collision. More specifically, the invention relates to an inflator assembly which generates gas to expand an airbag which cushions movement of a vehicle occupant in the event of a collision.
A known safety apparatus for restraining movement of an occupant of a vehicle in the event of a collision includes an airbag which is expanded by the flow of gas obtained from gas generating material in an inflator assembly. In order to protect the occupant of a vehicle adequately during a collision, the inflator assembly quickly generates a large quantity of gas and directs the gas into the airbag. The vehicle may be involved in a collision at a very high ambient temperature or at a very low ambient temperature. Thus, the inflator assembly must be able to provide the required quantity of gas to expand the airbag properly over a large range of ambient temperatures.
In very cold weather, the inflator assembly builds pressure more slowly than in warm weather so there is a tendency in cold weather for the airbag to be inflated too slowly or insufficiently to perform its intended purpose. Also, as the ambient temperature increases, the burn rate of the gas generating material increases. Consequently, at higher ambient temperatures, high pressures are created and the deployment velocity of the airbag increases. It is desirable that the airbag function uniformly at all ambient temperatures.
Also, the inflator assembly must be able to endure normal vibrations and shock loads to which a vehicle is subjected while being driven over many different types of roads. It is particularly important that the gas generating material in the inflator assembly be able to withstand severe vibrations and shock loads due to the vehicle encountering uneven roads and deep chuck holes.
Although the operating and durability requirements of the inflator assembly are very stringent, the safety apparatus must have a reasonable cost in order to obtain consumer acceptance. Thus, the components of the safety apparatus must be easily assembled and installed in a vehicle. However, once the inflator assembly has been installed in the vehicle, it must be capable of withstanding forces to which it is subjected due to driving of the vehicle for many miles for a relatively long period of time. If and when the vehicle is involved in a collision, the inflator assembly must be capable of quickly generating a volume of gas sufficient to inflate the airbag.